A semi-arid climate, semi-desert climate, or steppe climate is a dry climate sub-type. It is located on regions that receive precipitation below potential evapotranspiration, but not as low as a desert climate. There are different kinds of semi-arid climates, depending on variables such as temperature, and they give rise to different biomes.

Defining attributes of semi-arid climates

A more precise definition is given by the Köppen climate classification, which treats

steppe In physical geography, a steppe () is an ecoregion characterized by grassland plains without trees apart from those near rivers and lakes. Steppe biomes may include: * the montane grasslands and shrublands biome * the temperate grasslands, ...

climates (''BSk'' and ''BSh'') as intermediates between desert climates (BW) and humid climates (A, C, D) in ecological characteristics and agricultural potential. Semi-arid climates tend to support short, thorny or scrubby vegetation and are usually dominated by either grasses or

shrub A shrub (often also called a bush) is a small-to-medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees ...

s as it usually can't support forests. Les Falaises de Bandiagara

To determine if a location has a semi-arid climate, the precipitation threshold must first be determined. The method used to find the precipitation threshold (in millimeters): *multiply by 20 the average annual temperature in degrees Celsius and then **add 280 if at least 70% of the total precipitation falls in the summer half of the year (April–September in the northern hemisphere, October–March in the southern hemisphere) **add 140 if 30–70% of the total precipitation falls in the summer half of the year **add nothing if less than 30% of the total precipitation falls in the summer half of the year If the area's annual precipitation in millimeters is less than the threshold but more than half or 50% the threshold, it is classified as a ''BS'' (steppe or semi-arid climate). Furthermore, to delineate hot semi-arid climates from cold semi-arid climates, there are three widely used isotherms: either a mean annual temperature of , a mean temperature of in the coldest month, or a mean temperature of in the coldest month. A location with a ''BS''-type climate is classified as hot semi-arid (''BSh'') if its appropriate mean temperature is above whichever isotherm is being used, and a location with temperature below the given isotherm is classified as cold semi-arid (''BSk'').

Hot semi-arid climates

Hot semi-arid climates (type "BSh") tend to be located in the 20s and 30s latitudes of the tropics and

subtropics The subtropical zones or subtropics are geographical and climate zones to the north and south of the tropics. Geographically part of the temperate zones of both hemispheres, they cover the middle latitudes from to approximately 35° north and ...

, typically in proximity to regions with a tropical savanna or a

humid subtropical climate A humid subtropical climate is a zone of climate characterized by hot and humid summers, and cool to mild winters. These climates normally lie on the southeast side of all continents (except Antarctica), generally between latitudes 25° and 40° ...

. These climates tend to have hot, sometimes extremely hot, summers and warm to cool winters, with some to minimal precipitation. Hot semi-arid climates are most commonly found around the fringes of subtropical deserts. Hot semi-arid climates are most commonly found in Africa,

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

and South Asia. In Australia, a large portion of the

Outback The Outback is a remote, vast, sparsely populated area of Australia. The Outback is more remote than the bush. While often envisaged as being arid, the Outback regions extend from the northern to southern Australian coastlines and encompass a n ...

surrounding the central desert regions lies within the hot semi-arid climate region.Bureau of Meteorology – climate classification maps
/ref> In South Asia, both India and sections of Pakistan experience the seasonal effects of monsoons and feature short but well-defined wet seasons, but are not sufficiently wet overall to qualify as a tropical savanna climate. Hot semi-arid climates can also be found in Europe, primarily in southeast Spainhttp://www.aemet.es/documentos/es/conocermas/recursos_en_linea/publicaciones_y_estudios/publicaciones/2Atlas_climatologico/Atlas_Clima_Macaronesia___Baja.pdf and parts of Greece, Italy, Portugal and Cyprus. They are also found in parts of

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

, such as most of northern Mexico, the ABC Islands, the

rain shadow A rain shadow is an area of significantly reduced rainfall behind a mountainous region, on the side facing away from prevailing winds, known as its leeward side. Evaporated moisture from water bodies (such as oceans and large lakes) is carrie ...

s of

Hispaniola Hispaniola (, also ; es, La Española; Latin and french: Hispaniola; ht, Ispayola; tnq, Ayiti or Quisqueya) is an island in the Caribbean that is part of the Greater Antilles. Hispaniola is the most populous island in the West Indies, and th ...

's mountain ranges in the Dominican Republic and

Haiti Haiti (; ht, Ayiti ; French: ), officially the Republic of Haiti (); ) and formerly known as Hayti, is a country located on the island of Hispaniola in the Greater Antilles archipelago of the Caribbean Sea, east of Cuba and Jamaica, and ...

, most of the

Southwestern United States The Southwestern United States, also known as the American Southwest or simply the Southwest, is a geographic and cultural region of the United States that generally includes Arizona, New Mexico, and adjacent portions of California, Colorado, Ne ...

, and sections of South America such as the ''

sertão The ''sertão'' (, plural ''sertões'') is the "hinterland" or "backcountry". In Brazil, it refers both to one of the four sub-regions of the Northeast Region of Brazil (similar to the specific association of "outback" with Australia in English ...

'', the Gran Chaco, and the poleward side of the arid deserts, where they typically feature a Mediterranean precipitation pattern, with generally rainless summers and wetter winters.

Cold semi-arid climates

Cold semi-arid climates (type "BSk") tend to be located in elevated portions of

temperate zones In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout t ...

, typically bordering a humid continental climate or a Mediterranean climate. They are also typically found in continental interiors some distance from large bodies of water. Cold semi-arid climates usually feature warm to hot dry summers, though their summers are typically not quite as hot as those of hot semi-arid climates. Unlike hot semi-arid climates, areas with cold semi-arid climates tend to have cold and possibly freezing winters. These areas usually see some

snowfall Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water throughout ...

during the winter, though snowfall is much lower than at locations at similar latitudes with more humid climates. Areas featuring cold semi-arid climates tend to have higher elevations than areas with hot semi-arid climates, and tend to feature major temperature swings between day and night, sometimes by as much as 20 °C (36 °F) or more. These large diurnal temperature variations are seldom seen in hot semi-arid climates. Cold semi-arid climates at higher latitudes tend to have dry winters and wetter summers, while cold semi-arid climates at lower latitudes tend to have precipitation patterns more akin to

subtropical climate The subtropical zones or subtropics are geographical and climate zones to the north and south of the tropics. Geographically part of the temperate zones of both hemispheres, they cover the middle latitudes from to approximately 35° north and ...

s, with dry summers, relatively wet winters, and even wetter springs and autumns. Cold semi-arid climates are most commonly found in Mongolia, the Middle East and other parts of Asia and Western North America. However, they can also be found in Northern Africa, South Africa, Europe, sections of South America and sections of interior southern Australia (e.g.

Kalgoorlie Kalgoorlie is a city in the Goldfields–Esperance region of Western Australia, located east-northeast of Perth at the end of the Great Eastern Highway. It is sometimes referred to as Kalgoorlie–Boulder, as the surrounding urban area includ ...

and Mildura) and New Zealand (around

Alexandra Alexandra () is the feminine form of the given name Alexander (, ). Etymologically, the name is a compound of the Greek verb (; meaning 'to defend') and (; GEN , ; meaning 'man'). Thus it may be roughly translated as "defender of man" or "prot ...

Regions of varying classification

In climate classification, any one of three isotherms may be used to delineate hot from cold semi-arid climates — that of average annual temperature; or that of the coldest month, either or . The warm side of the isotherm of choice is classified as BSh, the cooler side as BSk. As a result of these differing definitions, some areas can have climates that are classified as either hot or cold semi-arid, depending on the isotherm used. One such location is San Diego, California (at its main airport). The city has cool summers for its latitude, due to prevailing winds off the ocean, so the average annual temperature is below ); however, winters are mild, with an average January temperature of , much closer to the coldest-month isotherm that separates tropical and subtropical climates than to the coldest-month isotherm that separates temperate and continental climates.

Charts of selected cities

References

External links

{{Koppen Grasslands Köppen climate types Plains Prairies